1. Field of the Invention
The present invention relates to a separator which diverts selected components of a fluid stream out of the main stream using force fields.
2. Prior Art
Force fields can be created by electric voltages and currents and are known as electric and magnetic fields. In both electric and magnetic separators, field gradients are produced which are changes in field strength with respect to position in the field volume. Electric fields produce forces on molecules or particles which have a net electric charge due to either missing or extra electrons. Magnetic fields will also produce forces on those molecules if they are also in motion across the magnetic field. Magnetic field gradients produce forces on molecules or particles which have a non zero magnetic susceptibility.
Previously patented separators using electric fields such as electrostatic precipitators, use a high voltage electric field to produce a corona between electrodes, which charges suspended particles and molecules in a fluid stream. The charging can take place upstream of the collecting fields, as in the two stage precipitation system, see U.S. Pat. No. 1,343,285, or the particle charging can take place at the collecting field, as in the single stage precipitator. The charged or ionized particles are then collected on a surface, which is in the fluid stream and which has a high gradient electric field surrounding it. The forces are Coulomb forces, which are proportional to the particle charge and intensity of the collecting field. The collected particles are then released from the surface by mechanical rapping.
The fundamental technical problem with this arrangement is reentrainment or rerelease of the collected particles into the fluid stream. Reentrainment may occur by direct scouring of the collecting electrode surface by the gas stream because the collecting electrode is in the main fluid stream. Or reentrainment may occur by redisposition of collected particles during rapping, again, because the collecting electrode is in the main fluid stream. See U.S. Pat. Nos. 342,548 and 895,729 and 1,132,124 and 1,343,285. To minimize reentrainment, previous precipitators were designed for low fluid flow velocities. This meant that they had to be large and expensive.
Previously patented separators using magnetic fields such as magnetic separators use a high strength magnetic field to produce magnetic gradients in the fluid flow. Magnetic materials in the fluid interact with the magnetic gradients because of the magnetic forces between them.
The intermittent type of magnetic separators such as the Kolm type, see U.S. Pat. No. 3,676,337, have the magnetic gradients randomly distributed throughout the volume of fluid flow and rely on the magnetic forces to embed the magnetic materials in the magnetic gradient areas. They must be turned off and periodically flushed to clean the magnetic materials away.
To overcome the requirement of periodically flushing, several continuous magnetic separators have been proposed.
Kelland in U.S. Pat. No. 4,261,815, discloses a separator apparatus in which a grid of fine ferromagnetic wires are arranged parallel to the flow of the fluid to be separated and a strong magnetic field is produced perpendicular to the wires and flow. The wires distort the magnetic field and result in a magnetic gradient around the wires which concentrates magnetic materials on opposite sides along each wires axis. As the wires near the end of the magnetic field there is a grid matrix for separation of the flows from each wire. This results in the need for small openings for each wire, which can become clogged and are difficult to fabricate.
In U.S. Pat. No. 5,169,006 I previously patented a continuous magnetic separator which employs rods comprised of alternating sections of nonmagnetic and ferromagnetic materials. This invention is an improvement on that patent because this invention includes other force fields besides magnetic, and is more efficient because the field gradients are continuous across the separation region.